Loud-speaker device



Feb. 24, 1931. WOQD 1,793,889

LOUD SPEAKER DEVI CE Filed June 21, 1927 INVENTOR 3;} 7 By Afiorneys,

Patented Feb. 24, 1931 ANDREW F. W001), 013 JERSEY CITY, NEW JERSEYLOUD-SPEAKER DEVICE Application filed. June 21,

This invention relates particularly to a loud speaker or loud speakingtelephone of the type in which sound is propagated from a vibratingsuriac directly to the free air without the intervention of a horn, theusual cone type loud speaker b an example of this type of apparatus.Nevertheless, certain "Features of my conical diaphragm and the conicalactuating means for transmitting motion to such diaphragm are appli ableto any form of sound reproducer employing a vibrating diaphragm, eitherwith or without a horn, and actuated by any source of vibrating energy,mechanical, electric or electromagnetic.

The object of the present invention is to provide a sound reproducingdevice which. to a high degree, faithfully reproduces a comparativelywide range of audible frequencies.

A further object of the invention is to provide a loud speaker device,which, for a given energy input, delivers an increased volume of sound.

The invention further contemplates in combination with a cone typediaphragm. a sounding board, against which the diaphragm actuatingmechanism preferably rests, so that the reaction from the forces againstthe diaphragm will act upon said sounding board, and in the preferredcon struction the invention provides a second sounding board spacedapart from said first mentioned sounding board to provide a resonant airspace therebetween.

Another object of the invention is to provide a conical actuatingelement through which vibration is transmitted to a larger conicaldiaphragm at points removed from the apex of the latter. 7

The present invention to increase the efiiciency of the cone type loudspeaker by the combination of two conical or dished diaphragms ofsomewhat different conical angles, whereby, although the members beconnected together at a point, there will, nevertheless, be providedbetween them an. air space, the volume of which expands radiallyoutward.

Another object is to provide a conical or 1927. Serial No. 200,379.

dished diaphragm, the marginal or basal edges of which are so shaped asto provide a plurality of areas which are not fully supported by thecentral conical area but extend th efrom, said areas therefore, beingmore ilei .ble than if they were connected by portions of the generalconical surface.

Further objects oi the invention will be apparent from the followingdescription, in which reference is had to the accompanying drawings, inwhich Figure l is an axial cross-section of loud speaker device having adouble conical diaphragm and a conical actuating means for saiddiaphragm.

a plan view of a loud speaker construction to the device shown d 2,except that the diaphragms and instead of star- 1 Figs. 1 L v o 1sounding boards are circinar shaped.

Figs. 4 and o are and central vertical cross-sec elv a plan view .11 ofa modidished dia respect weaker h av! 11 tied form of lone. phragm.

Jigs. 6, 7 and 8 are plan views of dia- --ragms according to the presentinvention ng differentmarginal contours. Fig. 9 is an axial ross-sectionof a phonoraph reproducer employing a conical diahragm actuated througha smaller conical riaphra Fig. 10 shows a telephone receiver having aconical diaphragm actuating element.

Referring to the embodiment shown in Figs. 1 and 2, the loud speakingdevice comcated in dotted lines in Fig. 2. It will be 1 understood thatthese flexible portions comprising the points of the star-shapeddiaphragnis are not flat, but to av considerable degree partake of theconical contour of the central portion of the diaphragm because theyform a part of and extend therefrom;

This is desirable, because while a certain degree of flexibility inthese areas greatly improves the quality of reproduction, neverthelessthey must have a certain strength or rigidity in order to efiiciencypropagate fibrous substance, such as paper, parchment I or very lightwood, or the diaphragms may be made of thin aluminum sheets. In fact,any material that is light and relatively strong may be employed. Thebest results liave been obtained with stiff paper. I

The conical actuator 7 which is connected to the vibrating" member ofthe electromag netic unit,'is1 in itself a conical diaphragm, its basaledgesbeing'preferably flanged to provide an annulus 8 which is cementedto the inner or concave face of diaphragm 1. This arrangemen provides anenclosed air space 9 between the actuator and the diaphragm l which isbelieved to contribute a desirable resonance effect. An importantadvantage of this arrangement, however, is had through the applicationof the vibrating energy to the major diaphragm l at points removed fromthe apex thereof. The direct mechanical vibration from theelectromagnetic unit transmitted through the conical actuator 7 to themajor diaphragm 1 and acts directly upon such diaphragm through theannular connection. 8. This arrangement results in a more positive andeffective action of the unit upon the diaphragm 1, so that thereproduced sound corresponds more closely to the applied vibrations thanin diaphragms where such vibrations are applied at a single centralpoint on the diaphragm.

Furthermore, the opposite disposition of the conical diaphragm and tscon cal actuator provides the additional advantage that when theactuator is moving to the left, and

consequently having its maximum. rigidity I through the inherentself-supporting effect of a conical surface, the diaphragm which itactuates, because of its'opposite conicity, is On the reverse movement,the

major diaphragm 1 is the more rigid and the coniealactuator less rigidbecause it does not receive the inherent bracing effect of a conicalsheet being stressed to flatten or expand it, and thus a compensation ishad which tends to render the opposing phases of any complete wavemovement similar. The conical bracing effect referred to is due to theto destroy to a considerable extent its rigidity with respect to suchforce. For example, a para sol not latched in the open position will befound to strongly resist a force tending to open or flatten it beyond acertain point determined by its design. Nevertheless, a very slightforce acting in the opposite direction will cause the collapse orfolding up of the ara sol.

' The electromagnetic unit is preferably mount-ed directly upon the faceof a sounding' board 15 so that the mechanical reaction of vibrating theconical diaphragms is transmitted to such sounding board; This soundingboard may be of spruce or other suitable resonant material, and shouldbe somewhat larger than the largest of the diaphragms mounted in frontof it. The sounding board effect is further increased by mounting to therear (or to the left, as shown in Fig. 1) of the sounding board 15, asecond sounding board 16, .he two being spaced apart to provideresonating chamber 17 as shown. The

boards are connected together near their edges by pins 18, and when twosounding boards are employed, the one nearest the diaphragms ispreferably fenestrated to provide openings 19 through which sound wavesfrom the rear of the diphragins may pass directly to the resonancechamber 17. The

mounted on the rear of thesounding board 16, so that it may be hungagainst the wall, and this bracket, together with the small fittings 21,serve to hold the sounding board out of contact ith the wall so that itis free to vibrate over the greater part of its central area. The loudspeaker devicelmay,of

course, be mounted uponv a pedestal. This pedestal comprises a weightedbase 23 having an upright column 24, which is threaded into a socket 25concealed between the two sounding boards. If it is desired to hang theloud speaker against the wall, the'pedestal is thus readily removed.

In certain types of electromagnetic units for-loud speaker diaphragmsthe actuating pin 6 is sufficiently rigid to permit of the mounting ofone or more diaphragms there on, the diaphragms being supported solelyby such pin. l/Vhere multiple diaphragms are to be employed, however, itis preferable toprovide other means of support, and such, support shouldbe designed to provide the utmost freedom of movement for the'dia deviceis provided with a hanger bracket 20 phragm. To this end, according tothe pres ent invention, the multiple diaphragm arrangement illustratedin Figure 1 is suspended upon a wire or other flexible member 26 from ab r 27 extending forwardly from the sounding boarc The flexible strandis preferably attached to the inner diaphragm 1, as means of a rivet 28a point immediately above the center of gravity of the connected cones1, 2 and '7. By this arrangement the actuating pin 6 is entirelyrelieved of the duty of supporting any part of the weight of the cones.The suspending wire may be adjust ably secured to the rod or post 27 bymeans of a set screw 28 which clamps the wire in any desired adjustment,the wire sliding free through the vertical bore 28 when the said screwis loosened.

In the preferred construction, rod 27 extends through the two soundingboards 15, 16, thus providing in a single element the spacing post 18which maintains the sounding boards in proper relationship and also thesupport for the diaphragms. The por tion 18 of the rod 27 which liesbetween the two sounding boards is somewhat enlarged to provideshoulders against which the sounding boards are clamped. The rod isthreadeo at either side of such enlarged portion, and the left-handsounding board 1) is clamped in place by a nut 29; the righthandsounding board is held in place by means of the fitting 20 which isthreaded onto the end of the rod, the said fitting providing the eye orother suitable means for hanging the loud speaker against the wall.

In Fig. 3 there is illustrated a loud speaker similar in every respectto the embodiment illustrated in Figs. 1 and 2, except that thediaphragms 1 and 2, and also the sounding boards 15, 16, are roundinstead of starshaped, such diaphragms therefore, being of theconventional cone type. While with sucn an arrangement the advantagesdue to the salient areas 4 and 4 of the star-shaped diaphragm are nothad, nevertheless, the application of a conical actuator to a conediaphragm of the usual type effects improve ment in the quality ofreproduction in such loud speakers.

The combination of two conical diaphragms, the surfaces of which areinclined at different angles but in the same angular sense fromtransverse plane, will be found to favorably affect the quality ofreproduction. While in the preferred construction the cones are directlyconnected together at their apexes, very satisfactory results can be hadby combining two cones of similar shape and spacing them apart toprovide an air chamber between them, the only absolute requirement as tothe disposition of the cones being that their surfaces slope in the samesense, though not necessarily in the same degree, from a planetransverse to the conical axis,that is to say-the one cone, at least inpart, projects within the second cone instead of the cones beingarranged in opposition one to another as has hitherto characterizedcertain types of double cone loud speakers. It is not essential thatsuper posed surfaces of the two cones diverge in the radial direction inorder to provide an expanding tone chamber between them, because thevolume of an annulus between the two cones at different radii willincrease according to the squares of such radii, even though the conesbe of similar taper or conical angle. Nevertheless, it is preferred tomake the conical angle of the inner cone 1 somewhat more acute than thatof the outer cone 2 so that a still further radial expansion ispermitted.

In Figs. 4 to 8 inclusive are illustrated loud speaker devices accordingto the present invention, in which the principle of employing a conicalor dished diaphragm having salients of various forms extending from thecentral conical or dished portion is shown The crevice illustrated inFigs. 4 and 5 com prises a dished diaphragm which is shieldshaped, theflexible salients being provided at the points 31 and 3:2. The diaphragmis lirectly actuated by the electromagnetic unit 33 at a point 3a, whichcoincides with what may be termed the axis of generation of the somewhatspherical form of thesurface. In this modification the actual form ofthe diaphragm surface is that of a cone, the apex of which has beenrounded off, as indicated in Fig. 3. A dished diaphragm of this contourmay be readily formed by radially.

slitting a conical diaphragm towards its cen ter and then pressing thesegments thus formed into the desired rounded contour. This operationwill cause the margins of the segments to overlap, and these overlappingmargins 35 are cemented together. If ductile material is used for thediaphragm, it may, of course, be pressed or drawn into the dished formwithout cutting. The loud speaker unit 33 in this construction ismounted directly upon a sounding board 37 in the manner hereinbeforedescribed. In the present instance only single sounding board isemployed, this board oeing provided with a hanger ring 39 and posts 10,by means of which the sounding board, when hung against a wall, is heldaway therefrom to permit its free vibration and also to afford aresonant air space bet veen itself and the wall. diaphragm shown in Fig.6 is a further modification in which salients 42, of greaterflexibility, are formed by shaping the marginal edges of the conicalsurface to provide rela tively narrow projecting areas bounded by foursimilar arcs 43.

The diaphragm 45 illustrated in 7 pro videsin still another formflexible salients 4:6,

The

, acteristic is also present in the 47 and 48, the three types ofsalients each differing arena the other, so that the symmetry of thediaphragm with respect to a horizontal transverse Xis, is destroyed.This chardevice illustrated in Figs. 4 and 5 and results in a tendencyto eliminate objectionable periodic defects-of the diaphragm."

The diaphragm illustrated in Fig. 8 is more properly described spyramidal han conical, and its apex is asymmetrically disposed withrespec to any possible that may be chosen. The basal edge of thediaphragm forms substantially a rec-tangle, the corner areas of whichprovide flexible salients 50,51, 52 and 5,3, which extend outward beyondthe central pyramidal portion.

In Fig. 9 there is illustrated a phonograph reproducer employing adiaphragm 60, which is acted uponby a conical actuator 61, according tothe; present invention. Mechanical vibrations are transmitted from thesurface of the record through a stylus'bar 62 in the usual manner, butthis stylus bar, instead of being attached directly to the diaphragm 60,is connected to the apex 63 of the conical actuator 61 The diaphragm isof conical form and may be made of thin aluminum sheet, the.

conical actuator being formed of the same material and having an annularflange 64s which is connected to the diaphragm. The

phragm 70, preferably formed of mica, is

employed. Cemented to the rear of this dia phragm is an actuating'cone71, which may be made of parchment. The apex of this cone is flattenedto receive an iron armature 72, which is acted upon the telephoneelectro magnets 73. Diaphragm 70 is flexibly mounted at its edgesbetween suitable gaskets 74.

A telephone receiver of this type is very sensi-' tive. The micadiaphragm can be made relatively thin because it is greatly strengthenedby the parchment cone 71, and the total vibrating mass of the diaphragmand actuating cone will be materially less than that of the usual irondiaphragm employed in telephone receivers. It will be seen that theprinciple of. imparting vibrating energy to the larger diaphragm throughthe actuating cone,

about an annulus removed to a considerable. extent from the center ofsuch diaphragm, corresponds to the underlying prlnciple of phragms,

the loud speaker device illustrated in Figs. 1 and 2, but while smalldiaphragms such as are employed in telephone receivers, give very goodresults when made flat, in the large diaphragms necessarily employed inloud speakers, wheresuch diaphragms act directly upon unconfined air,the conical form of diaphragm is to be preferred.

While various embodiments and modifications of my invention have beenhereinbefore described and illustrated, it is to be understood thatthese are merely illustrative and that the i vention may be otherwisevariously modified and embodied without departing from the spiritthereof, as set forth in the following claims.

W hat 1' claim is:

l. A sound reproducer comprising a substantially conical main diaphragm,a smaller opposed actuator diaphragm basally connected thereto in suchmanner as to provide substantially enclosed. air chamber therebetween,and actuating means adapted to apply vibrations to said diaphragmthrough said actuator diaphragm, said. main diaphragm having a totalarea at least twice as great, as the area of said actuator diaphragm.

' 2. A sound reproducer comprising a substantially conical diaphragm anda hollow conical actuator element adapted to transmit vibrationsthereto, said conical element engaging said diaphragm in an annulusaround the diaphragm apex, the diameter of said annulus being materiallyless than the diameter of the diaphragm, and the said diaphragm andactuator element constituting the walls of a substantially closed airchamber thereb-etween. V r r 3. A loud speakerhaving a plurality ofco-axially disposed interiitting conical diathe apex portions of whichare connected together, the inner diaphragm being more sharply taperedthan the diaphragm surrounding it whereby a radially outward expandingair chamber is provided between them, and actuating means for vibratingsaid and connected to the concave face of said inner diaphragm, and anactuating unit connected near the apex-of said actuating dia phragm andadapted to applyvibration to the latter.

5. A loud speaker according to claim 3, further characterized in thatthe said diaphragms are mounted 1n frontof a sounding:

board and spaced apart therefrom to permit the free egress of soundbetween said diaphragms and said board. r i

'6. A loud speaker according to claim 3,

further characterized in that the said dia-...

phragms are mounted in front of a soundi...

board with the basal portion of the outer or phragm approaching the saidsounding be? 1 .1]:

but being separated therefrom to per free egress of sound between s 'dd' and an actuating i so ling board, and connected to smaller conicaldiaphragm lying larger diaphragm, whereby produced l y unit are trdiaphra through c smaller one.

7. A loud spealzer to claim further characterized in that at L ast oneof said diaphragms is shaped to provide salient areas ezrtei dingmaterially beyond the central conical area, a sounding board spacedapart from the basal portion of the said diaphragms, an actuating unitmounted on said sounding board and an opposed conical actuatingdiaphragm fastened on the concave face of said inner diaphragm andadapted to transmit vibrations from said unit to said inner diaphragm.

8. Aloud speaker comprising a conical diaphragm, a substantially fiatsounding board, means to actuate said li phragm, said means beingmounted directly a ainstsaid sounding board, the said conical diap ragmbeing disposed with its basal edge ad acent to but separated from thesaid s ding bears, the apex of said diaphragm being directed away tromsaid board.

9. A loud speaker according to claim 8, further characterized in that asecond substantially flat sounding board is mounted to the rear of thesaid first-mentioned sounding board whereby to provide a sound chambertherebetween, said chamber permitting free egress of sound parallel tothe plane of the sounding boards.

10. A loud speaker according to claim 8, further characterized in thatspacing means are provided to hold the main area of the sounding boardaway from a wall surface against which it may be hung, whereby to permitfree vibration of the board over the greater part of its area and freeegress of sound from between the rear of the board and the wall againstwhich it may be mounted.

11. A sound reproducer comprising a diaphragm having a central concaveand substantially smooth portion and a plurality of salients projectingfrom said central portion, said salients forming continuations of thesloping surfaces of said central portions and providing diaphragmsurfaces of substantial area which are more flexible than if they wereincluded in the continuous central area of the diaphragm, and actuatingmeans engaging said central portion to vibrate said diaphragm.

12. A sound reproducer according to claim 11, further characterized inthat the said actuating means for vibrating said diaphragm is adaptedalso to provide the required diaphragm support, whereby the outerportions of the said diaphragm salients are permitted free andunobstructed movement.

13. A loud speaker comprising a vibrating diaphragm having asbstantially smooth conical contour, the basal part of said conicaldiaphragm having a plurality of outer portions at a distance from theapex of the cone, the edge of the said conical diaphragm being formed soas to connect said portions by lines which approach the apex of thediaphragm at points between said outer portions, whereby the said outerportions are rendered relatively flexible as compared with the centralportion of the diaphragm.

14. A loud speaker comprising a vibrating diaphragm having asubstantially conical contour, the basal part of said conical diaphragmhaving a plurality of outer portions of substantial area, the edge ofthe cone being formed so as to connect said portions by lines whichapproach the apex of the cone at least as near as would straight linesconnecting said outer portions, whereby the said outer portions arerendered relatively flexible as compared with the central portion of thediaphragm.

15. A loud speaker comprising a concave diaphragm,the surface of whichslopes on all sides from an apex to a surrounding basal edge,the basalpart of said diaphragm having relatively flexible outer portions ofsubstantial area, the said basal edge being formed so as to connect saidouter portions by marginal lines which have a maximum approach to thesaid apex at least as great as would straight lines connecting saidouter portions, and means to centrally vibrate said diaphragm.

16. A loud speaker comprising a vibrating diaphragm, said diaphragmhaving a substantially smooth conical contour, the basal edge of saidconical diaphragm having a plurality of symmetrically-arranged terminalpoints, said basal edge connecting said terminal points by lines whichapproach the apex of said conical diaphragm a suflicient dis tance atpoints intermediate said terminal points to provide the diaphragm with aplurality of salient portions of substantial area which are materiallymore flexible and easier to vibrate than if they mutually formed a partof a continuous conical surface.

In witness whereof, I have hereunto signed my name.

ANDREW F. WOO-D.

